HPV-caused mouth and throat cancers are a new epidemic among men -- one that people aren't fully aware of, according to cancer experts.

Human papillomavirus is well-known as the cause of cervical cancer in women. But the number of men who develop oral and throat cancers from an HPV infection has increased over the past several decades to "epidemic" status, said Dr. Eric Genden, professor and chair of otolaryngology at Icahn School of Medicine at Mount Sinai Hospital.

About 12,000 new cases of cervical cancer are diagnosed in the U.S. each year, according to the American Cancer Society, while the number of oropharyngeal cancers -- affecting the back of throat, base of tongue and tonsils -- in both men and women totaled around 12,660 in 2010, with an estimated 75 percent caused by HPV.

The possibility that Michael Douglas' throat cancer, which the actor was diagnosed with in 2010 and overcame more than two years ago, was caused by HPV is "not a blip on the radar," Genden said. "This is something that should be a discussion point to make people aware of their risk."

Here are some answers to common questions about HPV and oropharyngeal cancers.

Who gets HPV and how?

HPV is transmitted by "having contact with skin flakes with the HPV virus on it -- primarily through sexual transmission," said Dr. Marshall Posner, director of the Head and Neck Oncology Center at Mount Sinai Medical Center in Manhattan and HPV cancer researcher. "It can be transmitted from fingers, saliva, genitalia. Any kind of intimate physical contact will transmit the virus," Posner told the Daily News.

A higher number of oral sex partners increases the risk of contracting an oral HPV infection, Genden said. But HPV is so common that the vast majority of sexually active people have been exposed, no matter how many partners they have had.

"In general, 90 percent of the population has been exposed to HPV, and 10 percent of those harbor a chronic viral illness," Genden said. The 10 percent have a heightened chance of developing cancer and passing the cancer-causing strain to partners, he added.

That said, partners of people with cancer caused by HPV do not necessarily have to worry about getting cancer themselves. A study presented Saturday at the American Society of Clinical Oncology's annual meeting found spouses of oral cancer patients had no greater risk of developing cancer than the general population.

Does HPV always cause cancer?

There are more than 40 types of HPV, according to the Centers for Disease Control and Prevention, and not all of them are cancer-causing. In addition to cervical and oral cancers, HPV can also cause cancer of the vagina, vulva, anus, penis, head and neck, as well as noncancerous genital warts.

Most people clear an HPV infection on their own. There is no way to tell who will clear the disease and who will develop cancer, according to the CDC, but immune-suppressing influences such as smoking and chronic stress are thought to play a role.

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Cancer from HPV can take decades from the time of infection to develop, which means most people with an HPV-caused cancer were infected with the virus much earlier.

While HPV can be detected on the cervix by a pap smear, there is no corresponding test to screen for oral or other types of HPV infections. Because of this, both men and women may pass HPV back and forth without knowing it.

What are the signs of oral cancers?

Oropharyngeal cancer often forms in the lymph tissue at the base of the tongue and on the tonsil. Common signs include protracted sore throat and pain or difficulty swallowing. Tumors may also develop on the neck if the cancer has spread to that area.

The risk of developing oral cancer from an HPV infection is "really quite significant," Genden said. "People say don't smoke tobacco, or you're going to get cancer. But the cancer risk from smoking is 17.5 percent higher than the general population. If you have chronic HPV, your risk of developing cancer is 234 times the normal population."

What about the HPV vaccine?

HPV vaccines such as Gardisil and Cervarix prevent all types of cancers caused by HPV. It is important to receive the vaccine before becoming sexually active, as it will not protect against any strain of the disease a person has already been exposed to. The CDC recommends both girls and boys be given the vaccine series at ages 11 and 12 or as early as 9. Older men and women may also receive the vaccine through age 24, Posner said.

According to the CDC statistics from the 2011 National Immunization Survey - Teen, which assesses vaccination coverage among 13- to 17-year-olds, 53% of girls had received at least one dose of the HPV vaccine and 35% had received all three doses in the series.

Only 8% of boys had received at least one dose -- a number that's expected to go up, because the vaccine has been routinely recommended for boys only since 2011, a CDC representative said.

Some parents have been reluctant to vaccinate their children since the new shot became available -- and boys in particular, because their HPV-related cancer risk is less recognized.

But not doing so is a mistake, Genden said.

"It's critically important to get vaccinated," Genden said. "Boys need to be, and girls need to be. And OB-GYNs need to be aware, if a patient has an active HPV infection, they need to be very careful about actions that can transmit it."